The present invention relates to implantable electronic and electrochemical medical devices and systems, and more particularly to a movable contact locking connector system for use with such devices and systems. Such connector system provides easy lead insertion, a reliable means to retain an in-line lead in a connector and ensures effective electrical connection between lead and connector contacts. The connector system provides these features through a simple design avoiding complexity.
Implantable electronic medical devices and systems have been in use for the past 20 years or more. One of the earliest implantable medical devices to be implanted in a patient was the cardiac pacemaker. Other implantable electronic devices have included neurostimulators, i.e., electrical stimulators designed to stimulate nerves or other tissue, sensors for sensing various physiological parameters or physical status of a patient, and therapeutic-delivery devices, e.g., pumps for delivering controlled amounts of medication. In more recent years, a tiny implantable cochlear stimulator has been developed that allows patients who are profoundly deaf to experience the sensation of hearing. Other tiny implantable sensors and neuro-stimulators are under development that will enhance the ability of a patient who is a recipient of such sensors or stimulators to walk, or to see, or to experience the use of other lost or impaired body functions.
Most of the implantable medical devices and systems described above require that at least one electrical lead be connected thereto in order for the device or system to perform its intended function. Such lead typically includes a plurality of insulated conductors, or wires, through which electrical signals may be delivered or sensed. At an end distal from an implantable electronic device, each of the insulated conductors usually terminates in one or more electrodes designed to be in contact with body tissue. A Spinal Cord Stimulation (SCS) system, for example, has an electrode array adapted for insertion into the spinal column of the patient. Such electrode array typically employs a multiplicity of electrode contacts, each of which must be individually electrically connected to the pulse generator circuitry housed within an Implantable Pulse Generator (IPG). The lead associated with such spinal cord stimulator thus carries the individual conductors that electrically connect the respective electrodes, to the implantable pulse generator, thus making up the spinal cord stimulation system.
In-line leads are often chosen to connect an electrode array to an implantable electronic device. The contacts of an in-line lead are spaced-apart rings on one or more ends of the lead. An important benefit of such in-line lead is that when the lead is used with a ring type electrode array of similar diameter, the lead and array combination may be inserted into a patient""s spinal column using a large gauge needle. However, the use of a lead with such in-line male connector with a simple push-in female connector is limited by the ability to push the lead into a female connector passageway. The problem of in-line lead insertion has been addressed by U.S. Pat. No. 5,843,141 issued Dec. 1, 1998 for xe2x80x9cMedical Lead Connector System.xe2x80x9d The ""141 patent uses a tool to pull the lead end into the connector. However, the requirement to provide good electrical contact between the contacts on the lead and the contacts in the connector, and the need to provide a means for retaining the lead in the connector once inserted, work against easy insertion, and results in a requirement that the lead be sufficiently strong to resist tearing or stretching during insertion and extraction. Damaging a lead during the implanting or replacement of an implantable electronic device increases the complexity and medical risks associated with the required surgery. But, adding strengthening structure to the lead may be difficult and result in undesirable stiffening of the section of the lead where the lead exits the connector. What is therefore needed is an improved in-line connector system that allows easy insertion of an in-line lead into a connector, good retention of the lead once inserted, and reliable contact between the lead""s contacts and the connector""s contacts. Further, it is desirable that an improved in-line connector system, having these qualities, not compromise the beneficial properties which the lead would otherwise have.
The present invention addresses the above and other needs by providing a connector system with spaced-apart moveable contacts in the connector, and means for forcing the moveable connector contacts downward against spaced-apart lead contacts (for the purposes of this description, downward means toward the lead contacts, however, in actual use the connector may be arbitrarily rotated). The connector system may be integrated into the housing of an implanted device for the connection of a lead to the device. Advantageously, the connector system provides easy lead insertion, positive lead retention, and reliable electrical contact, without complexity.
In accordance with one aspect of the invention, there is provided a connector system including one or more spaced-apart moveable contacts in a connector, one or more spaced-apart lead contacts on an end of an in-line lead, and a means for applying downward force against the moveable contacts. When a lead in inserted fully into the connector passageway, the downward force causes the moveable contacts to move from a first position, wherein the moveable contacts are not pressing against the lead contacts, to a second position, wherein the moveable contacts are pressing against the lead contacts. When the movable contacts are in the second position, sufficient force is applied to the moveable contacts by the means for applying downward force, to both retain the lead in the connector, and to provide reliable electrical connection between the moveable contacts and the lead contacts.
It is also a feature of the present invention to provide a connector body made from a resilient material. One or more moveable contacts are molded into the resilient connector body so that, in the absence of force, the moveable contacts rest in a position which permits easy insertion and removal of the lead. When force is applied to the moveable contacts by the means for applying downward force, the moveable contacts press against the lead contacts, thus retaining the lead, and providing reliable electrical contact between the connector contacts and the lead contacts. When the downward force is no longer applied to the moveable contacts, the resilient nature of the connector body causes the moveable contacts to return to the first position, thus freeing the lead.
It is a further feature of the invention to provide a solid cam with solid lobes as a means for applying downward force. The cam may be rotated, and the solid lobes thereby apply force to the moveable contacts, which force results in the moveable contacts moving from the first position to the second position. A cam stop lug is provided on the cam that cooperates with a cam stop in the connector to limit the rotation of the cam. The positions of the cam lug and the cam stop are designed to allow the cam to rotate to a locked position slightly past centering the solid lobes on the moveable contacts. As the cam is rotated from an open position to a locked position, the cam solid lobe pushes down on the moveable contacts. As the cam solid lobes rotate downward and against the moveable contacts, the resisting force of the movable contacts against the cam solid lobes result in torque on the cam resisting the rotation from the open to the locked position. When the cam lobes are pointed directly down (i.e., towards the moveable contacts) the moveable contacts, the solid lobes, and the rotational axis of the cam are aligned. In this position there is no torque on the cam. When the cam is rotated slightly farther, the torque on the cam is reversed and is pushing the cam towards the locked position. A past center effect thus results that causes the cam to remain in the locked position until sufficient torque is applied to force the solid lobes past centering the solid lobes on the moveable contacts. In a preferred embodiment the cam is a straight shaft with solid lobes spaced along the shaft. In an alternative embodiment the cam is a simple wireform device.
In a first alternative embodiment of the means for applying downward force, a rod with bulged sections is inserted into the connector. When the rod is fully inserted, the bulged sections align with the moveable contacts, thus applying force to move the moveable contacts from the first position to the second position. Advantageously, the bulged sections may be radially symmetric which allows the rod to be inserted with arbitrary rotation. In a variation of this embodiment, the rod is captive with a first and second position, wherein the bulges are not aligned with the movable contacts in the first position, allowing easy lead insertion; and the bulges are aligned with the movable contacts in the second position, providing good lead retention.
In a second alternative embodiment of the means for applying downward force, a moveable actuator is captive within the connector. The actuator defines one or more bulges vertically aligned with the moveable contacts. The actuator is free to move vertically within the connector. A key is insertable into the connector through a key passageway above the actuator. When the key is inserted, a ramped surface on the bottom face of the key pushes downward against the actuator causing the actuator to move downward against the moveable contacts, and thus causing the moveable contacts to move from the first position downward to the second position.
In a third alternative embodiment of the means for applying downward force, the single actuator and moveable contacts combination is replaced by individual second actuators cooperating with each movable contact. When the key is inserted, the key""s ramped bottom surface pushes against the second actuators, thus causing the second actuators to move downward and push downward on the moveable contacts. The force of the second actuators on the moveable contacts causes the moveable contacts to move from the first position to the second position. In an alterative to this embodiment, the second actuators and moveable contacts are combined to form second movable contacts. The base of the second movable contact is resiliently molded into the connector body to allow vertical movement of the second moveable contacts and to retain the second moveable contacts in the connector body.